1. Field of the Invention
The present invention relates to a copier, printer, facsimile apparatus or similar image forming apparatus. More particularly, the present invention relates to a method of positioning image forming means for forming toner images on an image carrier one after another by repeating development, image transfer, cleaning and so forth, and a positioning jig for practicing the same.
2. Description of the Background Art
One of conventional image forming apparatuses is implemented as a tandem color printer in which four image forming means assigned to yellow, magenta, cyan and black and each including an image carrier unit and a developing unit are arranged side by side. In such a color printer, toner images of different colors are respectively formed on image carriers included in the image forming means and directly transferred to a paper sheet, OHP (OverHead Projector) film or similar recording medium one above the other, completing a composite color image on the recording medium. Alternatively, the toner images may be transferred from the drums to the recording medium by way of an intermediate image transfer belt or body.
A problem with the color printer described above is that the dislocation of any one of the image forming means directly translates into a color shift. Another problem is that if an image carrier unit and a developing unit, for example, included in each image forming means are dislocated relative to each other, then a gap for development between the two units becomes irregular and results in irregular tonality. In addition, not only image quality is lowered, but also toner is caused to fly about.
In light of the above, Japanese Patent Laid-Open Publication No. 7-175322, for example, proposes to mount a plurality of developing units to a single plate and bias each developing unit with a particular spring such that a developing roller thereof adjoins an image carrier associated therewith. This proposal is directed toward a constant gap for development. However, when power is transmitted from a drive source to the developing unit, the developing unit oscillates and causes the above gap to vary. Should the bias of the spring be intensified to prevent the developing unit from oscillating, the developing unit would be difficult to mount or dismount.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication No. 7-140787.